TLP bonding of dissimilar FSX-414/IN-738 system with MBF-80 interlayer: The effect of homogenizing treatment on microstructure and mechanical properties

Abstract In the present work, the effect of homogenizing time and temperature on the mechanical properties and microstructural evaluation of dissimilar IN-738/MBF-80/FSX-414 TLP joints was studied. The joints were made at the optimum bonding temperature of 1150 °C and homogenized at 1175, 1200 and 1225 °C for 1–6 h. Light and electron microscopes were used to investigate the microstructure. To study the hardness and alloying elements concentration profiles across the joints, the microhardness test and Wave length-Dispersive x-ray Spectroscopy (WDS) analysis were used, respectively. x-Ray Diffraction was used for identification of the phases. Shear tests were performed to measure shear strength of the joints. The results showed that, after homogenizing treatment at 1200 °C for 3 h, undesirable phases in the joint region were eliminated markedly while these phases were stable after 1 h homogenizing at the same temperature. Recrystalization at the joint region close to the FSX-414 base metal was seen at this temperature. At the same region, homogenizing treatment at 1225 °C led to intercellular carbide dissolving and recrystallization. At this temperature, grain boundaries liquation and precipitation coarsening occurred. The results of shear tests showed that, the shear strength of the joints was enhanced by about twice after homogenizing at 1200 °C in respect to the as-bonded samples.